The present invention relates to a method and apparatus for the production of a continuous rod-like filler which consists of or contains particles of tobacco. Such fillers are draped into webs of cigarette paper or the like in cigarette rod making machines for the production of continuous rods which are thereupon subdivided into sections (e.g., plain cigarettes or cigarillos) of desired length. More particularly, the invention relates to improvements in a method and apparatus for the production of a filler which contains several types or blends of tobacco. Still more particularly, the invention relates to a method and apparatus for the production of a rod-like filler wherein a core of a first type of tobacco (which may be a natural, artificial (substitute) or reconstituted tobacco) is surrounded by an annular or tubular envelope or shell containing or consisting of particles of another type of tobacco.
U.S. Pat. No. 3,987,804 discloses several embodiments of a method of and several embodiments of an apparatus for the production of a tobacco filler having a core consisting of a first type or blend of tobacco and a tubular envelope which surrounds the core and contains a different second type or blend of tobacco. All disclosed embodiments of the method and apparatus share the feature that a first layer of particulate material which is to constitute the envlope is showered onto a suction-operated belt conveyor, that a relatively narrow stream of particulate material which is to constitute the core is showered onto the first layer, and that a second layer of particulate material which is to constitute the envolpe is showered over the stream and over the exposed marginal portions of the first layer. The just discussed method and apparatus exhibit the drawback that the position of the stream on the first layer is not fixed, i.e., such position cannot be determined and maintained with a requisite degree of accuracy. Attempts to ensure that the stream will be formed exactly midway or substantially midway between the marginal portions of the first layer include imparting to the exposed surface of the first layer a concave shape so that such layer resembles an elongated trough and is more likely to center the stream midway between the marginal portions. This greatly increases the initial and maintenance cost of the apparatus and renders the apparatus prone to malfunction because the formation of a first layer with a concave upper side or exposed side involves a corresponding deformation and guidance of the conveyor on which the first layer is formed.
The aforementioned patent further refers to the possibility of forming a relatively thin first layer on the suction-operated conveyor, thereupon narrowing the tobacco channel above the first layer and showering the material of the stream into such narrow portion of the channel, and finally showering particles of tobacco into a wider portion of the channel to form the second layer on top of the narrow stream and the marginal portions of the first layer. The utilization of a channel which has a wide portion for reception of the material of the first layer, which thereupon narrows to receive the material of the stream, and which widens again to receive the material of the second layer is not likely to contribute to operativeness of the apparatus because the narrow portion of the tobacco channel downstream of a wider portion invites the development of so-called stoppers, i.e., clogging of the tobacco channel with attendant lengthy interruptions of operation of the machine in which the apparatus is put to use.
On the other hand, the making of a tobacco filler from several blends of tobacco is often desirable and advantageous, for example, to conceal tobacco whose color or another characteristic is less desirable, to confine so-called short, discard or excess tobacco within the longer shreds of the envelope, to allow for more accurate approximation of the weight of plain cigarettes to the desired or optimum weight and/or for other reasons.